Water and Proteins

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High water content is ________ susceptible to microbial spoilage

freeze drying, keep, denature

process of going from solid straight to vapor phase (sublimation)

______ nutritional value of food

will not _________ proteins

hexagonal, empty

structure of ice is in __________ form

58% ______ space

freeze concentration

process that forms pure ice crystals that separate from bulk

leaves behind concentrated solid

water activity

measure of effective water concentration in a food

“available water” for microbial growth and reactions

activity, content

water_________ is a better predictor of food spoilage than water _________

sorption

moisture __________ isotherms

plot water activity vs. water content

1, tightly

moisture sorption zone ____

_______ bound water

not available for reactions

2, weakly

moisture sorption zone _______

________ bound water

swelling of food matrix

3, free

moisture sorption zone ______

_____ water

chem, physical and microbial changes

desorption

high moisture content exposed to reducing relative humidity

adsorption

dry material exposed to increasing relative humidity

hysteresis

change in behavior based on the direction of the process

.6

no microbial growth below ________ water activity

oxidation, barrier, collision

lipid __________ in potato chips

low aw → no _______ of water against reaction

high aw → greater mobility and increase _________ frequency

browning, frequency, excess

maillard ___________ in milk powder

low aw → low collision ________

high aw → water in __________, decreases reaction rate because it is a product

freezer, saturated, increase

best long term storage

nonaqueous components become ___________ in unfrozen phase

volume _________

additives

additional components that convert free water to bounded by hydrophobic/philic interactions

salt, carbs, proteins

increases, shift

water activity _________ with temperature

understand how moisture sorption isotherm will ______ with temperature

depression, ions

freezing point ____________

water interacts with ____ instead of forming ice

add sucrose/salt

simple

protein that was not enzymatically modified after synthesis

conjugated

covalently modified protein with nonprotein parts

nitrogen, energy, textural

main source of dietary ________

support protein synthesis and ________ production

structural and _________ component in food

9

there are ______ essential amino acids for humans

side chain

amino acids grouped by characteristics of the _______ ________

hydrophobic, polar, positive, negative, sulfur

L, D

____- isomer is common and natural

____- isomer is rare and cannot be utilized

ampholytes

compound that can act as a base or acid depending of the pH of the system

isoelectric point

pH where dipolar ions become electrically neutral

MSG, bad

monosodium glutamate (__________)

sodium salt of glutamic acid

common in Asian foods

no clear evidence of _____ effects

oligopeptide

2-10 AA in a chain

polypeptide

10-100 AA in a chain

protein

greater than 100 AA in a chain

condensation

_________ reaction forms H2O form peptide bond formation

primary, sequence

__________ structure of protein

________ of AA connected by peptide bonds

secondary, stable

________ structure of protein

alpha-helix

beta-sheets (more _______)

tertiary, fold, optimization

________ structure of protein

______ into 3D form

_________ of favorable interactions of AA residues and the environment

quaternary

______ structure of protein

more than 1 polypeptide chain connected

IMF between subuints

denaturation

the unfolding of a protein

can be reversible based on conditions

critical value

point at which a protein structure cannot revert back to stable structure during denaturation

temperature, water

high __________ is the most common denaturation

reversible if not a long time

_________ facilitate denaturization

pressure, HPP, irreversible, retention

hydrostatic ___________ used to denature

______ - food packaging process

_________ denaturization and damage to cell membranes

good _________ of nutrition, color and flavor

shear

denaturization done by shaking and whipping proteins

gel electrophoresis

used to measure molecular weight after denaturation

measures based on size

activity, solubility

cons of denaturation:

loss of _______ → binding sites are gone

loss of _______→ hydrophilic/phobic forces are gone

foaming, digestible

pros of denaturation:

improve _________ and emulsification

more _______ than regular proteins

texturization

process to transform protein from globular to fibrous structure

creates chewiness and elasticity

veggie proteins

gel, water

______ = continuous 3D network of proteins that traps _____

thermally, revert, settling

______ induced gelation

irreversible → thermally set and will not _____ back

reversible → formed upon cooling and _______

reaggregation

when proteins come back together to form a gel

transparent, opaque

for gels:

ordered network = ________

unordered network = _________

opaque, hydrophobic, insoluble

_________ gel has large amounts of ____________ AA

unordered network from _______ protein aggregates

transparent, hydrophilic, hydrogen

_______ gel has large amounts of ________ AA

ordered network formed by _______ bonds

opaque, transparent, manipulate

for gels:

near pI = _______ gel

extreme pH = ________ gel

can ____________ the pH to produce different textures

ionic, turbid

_____ strength (salt concentration) changes gel

increasing creates _____ gel (excess attractive forces)

dough, stress

______ formation of proteins is based on solubility

kneading induces _______ to denature protein

spiral, viscoelasticity, crosslinks

add water and knead dough to create beta-_____ in proteins

____________ of dough due to properties of beta- [] and SS ________

solubility, low, denature

protein __________ affected by pH (stay away from pI), ionic strength (____ levels good), temperature (not ________)

amphiphilic

molecule contains both hydrophobic and hydrophilic parts

migrate spontaneously to interface

foam

____ is made up of aqueous continuous phase and gaseous dispersed phase

water-air interface

foam ability

amount of foam formed at the interface

measurable quantity

foam stability

ability of protein to stabilize foam against gravity and other stressors

resistance to collapse

measure ½ life of foam

absorb, unfold, viscoelastic, stresses

basic requirements for foaming agents:

1. ability to rapidly ___ air-water surface

2. ability to rapidly _____ and reorient at surface

3. ability to form strong _________ film with neighbors

   1. withstand shocks and ________

pI, stability, ability

Foam and pH:

near ____ = lack of repulsive forces, foam ________ increases

other pH = good ________ but poor stability

globular

most __________ protein have increased foaming ability with increased NaCl (ionic strength)

emulsion

mixture of 2 or more immiscible liquids

EAI, size

emulsifying activity index (_______)

measure droplet _____ of emulsions

EC, oil

emulsion capacity (_____)

volume of ______ emulsified per gram of protein

ES, centrifugal

emulsion stability (________)

separation under _______ force

absorb, reorient, stable, solubility

Good protein for emulsifier:

1. rapidly _______ to interface

2. rapidly unfold and _______ at surface

3. form _______ film around all

4. anti stress

5. maintain protein __________

partial, flexibility

_________ denaturation improves emulsifying properties

increase _______ with unfolding

hydrolysis, peptide

protein _________ can improve solubility and other characteristics

break apart some _______ bonds to get desired product

partial

______ hydrolysis improves solubility, dispensability, foaming, emulsification

complete

________ hydrolysis breaks all peptide bonds to produce only AA

enzymatic

_______ hydrolysis cleaves peptide to free 1 carboxyl and 1 amino groups

incomplete

________ hydrolysis breaks some peptide bonds to leave polypeptide products

degree hydrolysis

percent of peptide bonds still intact

cleaved, total

Calculating degree hydrolysis:

n - # moles of peptide bonds ________/mole protein

nT - ________ # moles of peptide bonds/mole protein

H+

mole _____ released = moles peptide bonds hydrolyzed

NaOH

mole _______ consumed = mole peptide bond cleaved

improves

solubility _________ after hydrolysis

short, viscoelastic

________ polypeptides can’t form cohesive ___________ foam

higher

_________ MW creates higher gel strength

destroy, nonspecific

hydrolysis ________ active sites on proteins

reduces allergenicity

___________ are more effective

bitter, whey

hydrolysates are more __________

reason for ______ protein hydrolysates are most popular

cross-linking

form bond between two amine groups in a protein

also between SH groups

alkylation

blocks reactivity of SH and NH2 groups

alter pH and solubility

acylation

react with acid anhydrides

protein is more soluble

phosphorylation

occurs to OH and NH2 groups

increase electronegativity

sensitive to Ca ion induced coagulation

heating, oxidative, raw

________ used to inactivate microorganisms

inactivate enzymes that cause _____________ and hydrolytic changes

transform _______ food

moderate, enzymes

____________ heat (60-90, 1hr or less)

denature proteins, inactivate __________

PER, mass, intake

protein efficiency ratio (_____)

gain in body _____/ protein __________

high, pyrolysis, irreversible

_________ temperature treatment

racemization, __________ and protein crosslinking

most changes are _______________

racemization, and, reduce

partial conversion of L to D isomers

heating at alkaline pH _____ heating > 200C

___________ protein digestibility

lose, rate

in racemization:

_____ tetrahedral symmetry

________ depends on side chain and OH concentration

pyrolysis, >, mutagenic

heat in the absence of oxygen

heat ____ 200C

highly ___________ compounds (IQ)

cross linking, or, decrease

connect proteins through NH2 or SH groups

heat at alkaline pH ____ heat > 200 at neutral pH

____________ in digestibility (peptide bond btwn links hard to reach)

maillard, heating, reducing, activation

greatest impact on sensory and nutritional properties of food

occurs during _________ or storage

between ____________ sugars (glucose) and primary AA group

high ______________ energy

condensation, amadori

1st step of maillard rxn:

_______________ of carbonyl with amine

may cyclize or undergo __________ rearrangement

transforms, dehydrate, cleavage

2nd step of maillard rxn:

____________ to complex mix of intermediates and products

may ___________ - form HMF

may undergo ___________ - produce aroma aldehydes

polymerize, melanoidins

3rd step of maillard rxn:

reactive carbonyl and amino groups _________________

form mixture of dark-colored, insoluble polymers called ________________